1. Field of the Invention
This invention relates to collapsable tubes formed of synthetic resin materials.
2. Description of the Prior Art
To date, there are different collapsable tubes available for holding tooth paste, medicinal paste, paste food and the like. Most of these tubes, in the past, were formed of metal such as aluminium and such tubes had a disadvantage in that the body thereof was left ugly without returning to its original shape after having been compressed. Recently, collapsable tubes which are formed of synthetic resin materials have been in common use, which not only eliminate the aforementioned disadvantage of the prior known metal tubes but offer numerous advantages such as reduced cost and increased productivity. These tubes are constructed of synthetic resin materials that are sufficiently elastic to permit the body to return to its original shape after having been compressed. However, during the return process, air is allowed to enter into the body of the tube, tending to oxidize the substance contained therein as well as, when it is rapidly compressed, to cause a spattering of the substance due to the fact that it is forced to burst out with the air. Furthermore, because of the generally high permeability of synthetic resin to oxygen gas, water vapor and odor and their poor oil-resisting property, there is a tendency for the substance contained in such a tube to be adversely affected physically or chemically.